Spark-plttg



l. RYSTEDT.

SPARK PLUG.

` APPLICATIONEFlL-ED JUNE 4, i917. 1,371,058. i Patented Mar. 8, 1921.

b; l i m s y V UNITED STATES PATENT OFFICE.

INGEMAR RYSTEDT, OF DAYTON, OHIO.

SIPARK-PLUG.

Specification of Letters Patent.

Patented Mar. 8, 1921.

Application filed June 4, 1917. Serial No. 172,710.

To all whom t may concern.'

plugs therefor. The object of the invention is to improve the structure as well as the means and mode of operation of such devices, whereby they will' not only be cheapened in construction, but will be more eflicient in use, protected against breakage, compression-tight'J and unlikely to get out of repair. v y

A further object of the invention is to provide an improved insulating core of heat resistant material which will readily withstand extreme variation of temperature without crazing or cracking and to further pro` side elevation of the assembled spark plug.v

Fig. 2 is a longitudinal sectional view thereof. Fig. 3 is a longitudinal sectional view of a modification of the construction shown in Fig. 2. Fig. 4: is a detail view illustrating the method of'attaching the spark point to the central or insulated electrode.

Like parts are indicated by similar characters of reference throughout the several f head having the hexagonal or polygonal collar 2, a screw threaded projecting stem 3 terminating in an oval or dome end a andl on its upper side having a screw threaded boss 5. This main bushing is provided with a central straight or cylindrical bore for the insulating core. Adjacent to the extremity of the bushing stein 2 or the inner end of said head ortbushing the interior bore is provided with an interior groove or recess 7 forming a Cement pocket as hereinafter described. Inserted within the central bore of the bushing or head 1 is an insulating core 8 composed of-quartz or fused silica, shaped and proportioned to accurately fit the interior of the bushing or bore. With the present method of manufacture, such quartz or fused silica cores cannot be accurately manus factured to provide a gas-tight joint between the core and the bushing. To overcome the difficulty and provide a compression-tight joint, the exterior of the silica or quartz core 8 is generously coated with heat resistant cement of the porcelain cement type such as are now commonly in use. The annular groove or cement pocket 7 within the bore of the bushing is'also filled with such cementV or sealing material which by its adherence with the quartz or silica core and with the metal bushing, firmly and securely unites the said parts togethery to form a compression tight joint. Vhile the film of cement surrounding the core 8 has been shown in the drawing as of appreciable thickness, it will be understood that with an accurately proportioned core this film of cement will be extremely thin. serves to firmly unite the quartz or silica core 8 withthe walls of the bore of said bushing l, the primary purpose of the cement is vto fill any 4hollows or uneven or ununiform surfaces of the core 8, filling such depressions or surface markings to a uniform degree coincident with the walls of the bore of said bushing. Heat resistant cemeiits of the porcelain type especially prepared and adapted for uniting various materials with metal, are to be vhad under various trade or proprietary names. Such cements Vhile the cement filni unite not only with the metal but with the quartz or silica, forming with the latter a substantially homogeneous mass. Y The union of the body of cement within the pocket or` ahnular groove 7 ofthe bushing with the inserted quartz or silica core provides an interlocking bead or collar upon said core interengaged with the bushing in such a manner as to securely hold the core in position.

The quartz or fused silica of which the core 8 is manufactured possesses remarkable heat resistant properties and ya low coefficient of expansion whichv renders it particularly desirable for spark plug purposes. The coeflicieiit of expansion of this material is so extremely small, being approximately oneseventeenth that of glass, that it is enabled to withstand rapid changes of extreme degrees of temperature, without danger of breaking. It is likewise acidand chemical proof, resisting both acid and alkaline action at the ordinary temperature to which it is subjected in spark plug service. As an electrical insulator, quartz or fused silica is much superior to porcelain, mica, glassvand similar materials commonly used in spark plugs and has been given an extremely high rating in comparison with these materials by the United States Bureau of. Standards. This material is, however, extremely refractory and has a tendency when subjected to high temperature for a long period to become brittle. The present plug is designed to overcome this objectionable feature by affording protection to the insulating core 8 throughout its entire length in such a manner that it cannot be subjected to such force as to cause breakage.

In forming the core 8 it is provided with a central passage or bore proportioned to agree as nearly as possible in diameter with that of an electrode 9 to be passed therethrough. The electrode 9 forms one terminal of the ignition circuit. It is provided at its lower end with a collar or head 10 which abuts upon the inner end of the core 8. In order that the electrode 9 may accurately fit the bore or passage of the core 8 it isgen-V erously coated with the same character of heat resistant cement, such as' porcelain cement or other cement or sealing material of the same type and is then introduced within the passage or bore of the core where the coating of cement will securely unite with the core, forming a compression-tight joint. The outer end of the electrode 9 is screw threaded as at 11 to receive a binding nut 12. Screw threaded upon the boss 5 of the head or bushing 1 is a sleeve 13 having therein a plurality of orifices or openings 14. The outer end of the sleeve 13 is internally screw threaded to receive a plug or cap 15 of fiber, bakelite, rubber, composition or other insulating material which is provided with a central bore or pocket into which the end of the insulating core 8 projects, The plug or cap 15 is also provided with a central passageway through which the extremity of the electrode 9 extends. The end of the core 8 is coated with the same cement or one of like nature before being inserted in the bore or pocket of the cap or plug 15 and the latter is then screwed into place within the sleeve 13 whereupon the union of said cement with the fiber or other cap or plug and with the core firmly unites said parts and prevents their disengagement. The plug or cap 15 does not extend within the sleeve 13 into contact with the end of the boss 5, but there is left intermediate the boss 5 and the plug or cap 15 an intermediate annular space 16 surrounding the core 8 with which the openings or orifices 14 communicate. This space provides av Ventilating chamber through which air may readily circulate about the core 8 to dissipate the heat of said core. At its imier or sparking end the electrode 9 is bifurcated as shown at 18, the fingers of such bifurcation being bent outward and in reverse directions whereby they approach the rounded end 4 of the bushing 1. In Fig. 2 these sparking points` are shown integral with the electrode 9. In Figs. 3 and 4, however, the electrode 9 is shown as beingbifurcated at its extremity as indicated at 19. The sparking points in this instance. are formed of wire bent upon itself to a W- shape as at 20, the middle bight of Whichis engaged within the bifurcation 19 of the electrode 9a of Fig. 3; The sparking points are retainedby clenching or staking the fingers of the bifurcation 19 about the middle. bight of the spark point member.

The construction shownv in Fig. 3 differs' from that of Fig. 2 also, through the fact that the sleeve 13a-of Fig. 3 .is formed integral with the main bushing 1 in lieu-,ofbeing screw threaded upon the hub 5 as shown in Fig. 2. Likewise the insulating plug or cap 15ZL of the construction shown in Fig. 3, instead of being screw threaded within the sleeve 13a is merely inserted therein and the j upper endr of the sleeve is contracted or` clamped upon the plug or cap by a swaging operation.

The construction of the sparking points insures asuflicient arc or spark gap and by aording double spark points` reduces the difficulties due to fouling to minimum. The sparking points being opposed to the rounded surface 4 of the plug are afforded a large sparkingsurface which will not readily burn or pit. The core 8 of quartz or fused silica having high insulating properties' and with the further advantage of physical' resistance to high temperatures and temperature changes with a much lower decrease of insulating value with increase of temperature than is afforded by other insulatingr mediums commonly in use, together with the protection afforded to said corethrough the total inclosure thereof, provides aspark plug of high efficiency.

From the above description it will be apparent that there is thus provideda device of the character described, possessing the particular features of advantage before enumerated as desirable but which obviously is susceptible of modification in itsv form, proportion, detail construction or arrangement of parts, without departingfrom the principle involved or sacrificing any'y of,its1 advantages.

While in order to comply with thestatute, the invention has been described in language more or less specific as to certain structural features, it is to be understood that the invention is not limited to any specific details, but that the means and construction herein described com rise but one mode of putting the invention into effect, and the invention is therefore claimed broadly in any of its possible forms or modifications Within the scoe of the appended claim.

aving thus described my invention, I claim:-

A spark lug comprising a main bushing having a su stantially uniform bore, a tubu lar extension engaged with the bushing of greater internal diameter than the bore, a head engaged with said tubular extension, a core of insulating material extending through the bore of the bushing and the tubular extension and havin a nonyielding thrust bearin against sai head whereby longitudina movement of the core under the 1nfluence of compression and explosion Within the engine cylinder is resisted by said head, the strain of such thrust being transmitted thence through the extension to the main bushing, and an electrode inclosed within the core.

In testimony whereof, I have hereunto set my hand this 24th da of May A. D, 1917.

ING MAR RYSTEDT.

Witnesses:

H. P. WILLIAMsoN,

I. I. HAUER. 

